Electric tool.



No. 824,953. PATENTED JULY 3, 1905. P. SGHIEMANN.

ELECTRIC TOOL.

APPLIGATION FILED NOV. 7, 1904.

Aiiwmqy n4: NORRIS PETERS 170 WASHINGYON, D. c.

PAUL SOHIEMANN, OF DRESDEN, GERMANY.

ELECTRIC TOOL.

Specification of Letters Patent.

Patented July 3, 1906.

Application filed November 7, 1904. Serial No. 231.740.

To all whom it may concern:

Be it known that 1, PAUL SOHIEMANN, engineer, a subject of the King of Saxony, residing at No. 26 Kyfihauserstrasse, Dresden, in the Kingdom of Saxony, German Empire, have invented certain new and useful Improvements in Electric Tools, of which the following is a full, clear, and exact description.

The present invention relates to electric tools driven by the electromagnetic effect of coils; and its Object is to avoid the loss of energy, which is very considerable with this class of tools and which is mainly due to ex cessive sparking when switching the coils in and. out and also to the excessive heat gener ated in the tool partly by eddy-currents and partly by the large number of coils necessitated.

In order to render the present specification easily intelligible, reference is had to the accompanying drawings, in which similar figures of reference denote similar parts throughout the several views.

Figure 1 is a section through the toolholder Fig. 2, a diagram showing the arrangement of the coils and conductors, and Fig. 3 a longitudinal section of the ,contact making and breaking device.

The present construction is based on the following principle: In the first place the current is not interrupted when it is changed; but the two coils are arranged in series in the circuit and one of the two is short-circuited, so that the other will be effective. Then, again, each of the solenoid-coils is divided up into at least two parts, and by means of a peculiar switch device one part of the coil in uestion alternately plays the part of a resistance, so that the sparking energy is rendered. useful. I

Finally it is the object of the present invention to utilize the magnetic energy of the current present in the coils at the end of each stroke, thus not only effecting a saving of energy, but also avoiding sparking to a great extent. Thus if the circuit of an electric magnet is interrupted the magnetic energy must disappear. Physically, of course, merely a conversion of the energy can take place, and consequently at the point of interruption great heat develops, causin the sparking.

The armature or solenoid core 1 moves in the sleeve 2 in the well-known manner, in that it is alternately drawn into one or the other coil 3 or 4. At the end of the core 1 and insulated therefrom is a metal disk 5, which limits the stroke of the contact-slide 6. The latter consists of a sleeve having flanges at each end and is adapted to move on the contact-bar 7, consisting of a combination of several parts. This contact-b a1, which forms the essential feature of the switching mechanism, is composed of the contact 9, which, as will be seen from the diagram in Fig. 2, is connected to one end of the coil 8 and one of the current-feed conductors. It is further composed of the insulated contact-ring 10, connected to the center of the coil 3 and dividing this into two parts, and also of the intermediate contact 13. The contact 11 is connected with the other end of the coil 3 and with one end of the coil 1, while the other end of the latter is connected to the contact 12. The center of the coil 4 is connected to the intermediate contact 13. The contacts 10 11 12 13 are mounted 011 an insulating-sleeve on the core lat and insulated from each other, the said core being connected at one end to the current-feed conductors 15 and 16 and having an enlarged end forming the contact 9. The intermediate contacts thus divide the coils into two parts. These coils 3 and 1 could of course be further subdivided by employin further intermediate contacts; but this is hardly necessary, since with a single subdivision of the coils the mutual induction of the separate parts of the coil has the eii'ect of rendering the sparking very slight when switching around, and consequently uninjurious.

The switching mechanism operates in the following manner: As soon as the slide 6, for instance, leaves the contact 9 the current will pass through the coil 4 and through the left-hand half of coil 3, so that a current of magnetic lines of force is produced in the latter. Since this current, however, passes through the short-circuited right half of coil 3, a current will be produced simultaneously in this'latter, which will practically prevent the production of the lines of force. Thus it will be seen that the reacting tension on switching will be very slight, owing to the sub division of the spools per se and to the effect of mutual induction. The result will be the same with the other switching movements.

I claim as my invention- 1. An electric tool driven by solenoids and having subdivided solenoid-coils the parts of which are consecutively short-circuited.

2. An electric tool having a stationary con tact-bar and a series of contacts thereon and a contact-slide thereon and a solenoid-core to reverse the latter at the end of each stroke.

3. An electric tool having a contact-bar carrying all the contacts in a row thereon and having the feed-conductors in the interior of the said bar substantially as described.

In testimony that I claim the foregoing as my invention I have signed my name in pres- 1o ence of two subscribing Witnesses.

PAUL SCHIEMANN.

W'itnesses:

UNG'ER HIDMAN, CHEMNITZ H. SCHILLING. 

